Here's the deal. The Clean Sweep on its own doesn't restore full-range magically. Nothing does, BTW. But who cares? Just run the rear high-passed signal into the CleanSweep rear inputs, and ignore the orange "I didn't succeed at full-range" light, and it works fine - because your rear speakers shouldn't be running full-range anyway.
Yes, the rear signal is wacky. And if you dare say "well, it doesn't matter, it's just rears", then I will reply with "THEN WHY ARE YOU UPGRADING THEM?" in 50-foot-tall type.